1. Field of the Invention
This invention relates in general to certain new and useful improvements in joined winged aircraft, and more particularly, to aircraft of the type stated which employ dual airfoil structures invluding forward and aft pairs of wings structurally joined by members which also function to improve the aerodynamic quality of the aircraft.
2. Brief Description of the Prior Art
A number of prior patents including applicant's U.S. Pat. No. 3,942,747 have described joined wing aircraft. Most of the prior art designs are either deficient misdirected or inadequate. By way of example, the following patents have been considered:
U.S. Pat. No. 4,090,681 to Zimmer discloses an aircraft with two sets of wings which form a closed frame in front elevational view. All of the wings are both swept rearwardly with respect to the fuselage. In addition, the rearwardmost wings attach to the fuselage at a lower elevation than the front wings. While the aircraft in the Zimmer patent includes a tail fin, this tail fin does not structurally support the wing.
U.S. Pat. No. 3,981,460 to Ratony shows an aircraft design with sweptback and swept forward wings which are constructed so that they form a closed triangular or diamond-shape frame in front elevational view. However, in the Ratony patent, there is no tail fin employed to brace the rear wings.
U.S. Pat. No. 1,836,896 to Brown illustrates an aircraft which employes three sets of wings in a tripod-type arrangement. Two of these wings are described as being "substantially in the same plane". Hence, the dihedral angles of the two wings are equal or approximately equal, and the dihedral angles formed are small or zero. In addition to the above, the two pairs of wings form a diamond-shape in the top plan view. The additional, or the third pair of wings, incorporates a large dihedral angle in order to form the triangular configuration in front view. The two upper or coplanar wings have a common tip surface which is also coplanar with the upper wings. While this type of arrangement does produce a high strength to weight ratio, it nevertheless has very significant disadvantages due to the interference drag of the numerous joints which are required to connect the three wing elements.
U.S. Pat. No. 3,834,654 to Miranda discloses an aircraft construction which uses forwardly swept upper wings and rearwardly swept lower wings which are connected by vertical elements in order to form a rectangular (box) configuration in front elevational view. This construction presents various disadvantages in that the so-called "boxplane" configuration inherently has low structural stiffness against side forces due to the fact that it has no diagonal members. In the older types of low-speed bi-planes the structural stiffness against side forces was provided by bracing wires.
U.S. Pat. No. 2,576,294 to Geraci discloses a boxplane configuration, in which the members forming the box are curved thereby presenting convex outer surfaces in front elevational view. Each end of the box bulges outwardly. In addition, and in a manner similar to the aforesaid Zimmer patent, both the front and aft wings are sweptback so that in plan view a diamond shape is not formed.
U.S. Pat. No. 1,453,830 to Coakley also discloses an aircraft having a wing structure comprised of superposed wings which also form one or more diamond shapes in at least front elevational view. Coakley does not describe the use of a fin to provide a central vertical member for a diamond configuration. While Coakley does not describe a plan view of his aircraft wing configuration, it is clear that it cannot be diamond-shaped with only two wings since it is stated that the airfoils are superposed. Thus, they must have similar sweep angles.
British Pat. No. 508,022 to Warren and Young describes an aircraft configuration having sweptforward rear wings and sweptback front wings. The wings are joined by common tip surfaces, much in the same manner as the configuration in the Brown patent, supra. These common tip surfaces are coplanar or at least approximately coplanar with at least one of the wings.
French Pat. No. 42,428 to Hausson also discloses an aircraft in which the front wings are swept back and have a negative dihedral while the rear wings are swept forward and have a positive dihedral. Hausson states that his wings are connected at their tips, but the means of connection is not described though the drawings seem to indicate a common tip surface similar to the Warren and Young arrangement.
U.S. Pat. No. 4,053,125 to Ratony also discloses a joined wing aircraft where the front wings have little or no dihedral and the rear wing roots are not attached to the fin. In addition, a separate tail is illustrated and the wings overlap.